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This study presents the land cover map of the desert locust recession area in 2000, focusing on drylands using NDVI data and a classification procedure based on temporal profiles. The map identifies ten land cover classes, from bare areas to dense vegetation, with a focus on vegetation cover percentages and seasonal variations.
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GLC 2000 land cover map of the desert locust recession area First results E. Bartholomé, JRC Ispra M. Cherlet, FAO Rome
The desert locust recession area 19°W – 80°30’E, 46°N – 4°N Main focus on drylands
Input data • S10 NDVI for 2000 • Re-scaled in vegetation cover percentage • Soil effect removed (per-pixel method) • Temporal profile smoothed (see ad hoc presentation)
cover • Seasonality: max in summer or winter, or double seasonality 1/3 time Classification procedure Based on temporal profiles Rigid tresholds on: • Max vegetation cover in 2000 • Season duration
Rationale • Cover max • corresponds to max development of vegetation • Best correlates with above-ground biomass • duration Duration close to phenological definition, but time lag
100% 9 75% 6 8 4 10 50% 6 8 25% 5 7 2 10% 3 5% 1 1 3 6 9 12 months Classes Max cover 1 BARE AREAS 2 SPARSE HERBACEOUS VEGETATION - NOT ANNUAL - TBC 3 SPARSE HERBACEOUS VEG 4 CLOSED-OPEN HERBACEOUS VEG 5 SPARSE DECIDUOUS SHRUB AND SPARSE HERBACEOUS VEGETATION 6 OPEN DECIDUOUS SHRUB AND OPEN HERBACEOUS VEGETATION 7 SPARSE DECIDUOUS SHRUB AND SPARSE HERBACEOUS VEGETATION AND SPARSE TREE LAYER 8 OPEN DECIDUOUS SHRUB AND OPEN HERBACEOUS VEGETATION AND SPARSE TREE LAYER 9 CLOSED-OPEN DECIDUOUS SHRUB AND CLOSED- OPEN HERBACEOUS VEGETATION AND OPEN TREE LAYER 10 NOT DEFINED Growth duration The same applies for winter vegetation and double season growth
Close-up (1) Sarir (Libya) Irrigated agriculture
Close-up (2) Luxor (Egypt) double growing season
Close-up (3) Senegal - Mauritania
Observation 1 • Noise in the 3-5% cover range Haruj es Sawda Volcano (Libya)
Observation 2 • Specific year 2000 situation 1999-2000 2000-2001 Land cover map
Observation 3 • Cropland not detected per se: low % of surface
conclusions • The method seems efficient for dryland vegetation (bare soil correctly mapped!) • The method is sensitive to the specific year for very sparse vegetation • Some “soil contamination” • Need for regional analysis to label the land cover classes